This paper presents a dimensional synthesis method for designing wide-band quarter-wavelength resonator bandpass filters. In this synthesis method, an alternative lowpass prototype filter and the edge frequency mapping method are proposed and applied. The improved Kand J-inverter model with the exponent-weighted turns ratio is also proposed in order to incorporate the frequency dependence of inverters. Based on the edge frequency mapping method and the improved inverter model, an iterative dimensional synthesis procedure is then presented. As design examples, a four-pole rectangular coaxial bandpass filter with 63% fractional bandwidth is designed and fabricated. The simulation and measurement results show good equal ripple performance in the passband.